On GitHub, navigate to the main page of the repository.
To the right of the list of files, click Releases or Latest release.
Next to the release you want to use as your base, click Compare.
Use the "Compare" drop-down menu and select the tags you want to compare.
Article version: GitHub.com
You can compare release tags to see changes to your repository between different releases.
People with read access to a repository can view and compare releases.